Falling film evaporator of the rotating drum type



Feb. 8, 1966 w. RODENACKER 3,233,655

FALLING FILM EVAPURATOR OF THE ROTATING DRUM TYPE Filed April 8, 1963 2 Sheets-Sheet 1 RAW LIQUID H :4 SW g i 3 1 l 7 0 VJCUVM r C OIVDt'A SAT E INVENTOR.

WOLF RODENACKER ATTORNEYS Feb. 8, 1966 w. RODENACKER 3,233,656i

FALLING FILM EVAPORATOR 0F THE ROTATING DRUM TYPE Filed April 8, 1963 2 Sheets-Sheet 2 INVENTOR.

WOLF RODENACKER ATTORNEYS United States Patent Claims. a. 159-12 The invention relates to a film evaporator for liquids, using, as evaporator surface, a roller which is rotatably arranged inside an upright evaporator chamber and is wetted by the liquid, the evaporator surface forming a wedge-shaped gap with at least one body arranged in the evaporator chamber, the liquid being supplied under pressure into this gap and removed from it again under pressure.

The liquid is thoroughly mixed in these wedge-shaped gaps without requiring mechanical stirrer arms or the like.

In order to adapt the thickness of the layer on the roller, i.e. the rate of throughput through the evaporator, to the viscosity of the products being treated, the body which forms a wedge-shaped gap with the roller is constructed in accordance with the invention, as a blade which pivots about fixed spindles and which is curved concavely towards the roller and is resiliently supported on the inner Wall of the evaporator chamber.

In order to accelerate the flow of liquid from above downwards through the wedge shaped gap, particularly in the case of highly viscous liquids, the blade is provided with grooves arranged on the surface facing the roller and directed obliquely to the axis of the roller.

A constructional embodiment of the invention is shown diagrammatically in the drawing.

FIGURE 1 is a longitudinal section and FIGURE 2 is a transverse section through the apparatus. FEGURE 3 shows the gap on an enlarged scale. FIGURE 4 is a view from above on to the inner surface of a blade.

The raw liquid P, which may, for example, be a viscous liquid, is conveyed to the evaporator chamber through the connecting pipe 1 and carried into a gap 3 by means of a hollow worm 2. At this throttle point, the liquid is subjected to a certain pressure which should be above atmospheric pressure so that the thin layer evaporator chamber may also be operated with a vacuum. The liquid F passes through the annular gap 3 to a roller 4 where it is caught in wedge-shaped gaps 8 formed between the roller 4 and blades 5, and again and again distributed over the roller 4.

As shown in FEGURE 3, the liquid is stirred round in the wedge-shaped gap (arrow 6). Bubbles 7 present in the material separate off at the centre or" this movement owing to their upthrust and leave the material and enter the vacuum space 9. The liquid ill leaving the gap 3 is carried as a layer free from bubbles on the surface of the roller 4 where it is conveyed through the space 9. The blades 5 are swingably mounted at the top and bottom on the fixed spindles 11. The width of the wedgeshaped gap 8 may be adjusted as desired according to the viscosity of the liquid by means of springs 12 which provide a suitable force and which may be replaceable or may be adapted to be adjusted from outside.

In order to distribute the viscous liquid rapidly over the whole length of the roller and to obtain a good rate of throughput through the apparatus, the blades 5 are provided with grooves 13 directed obliquely to the axis of the roller, as shown in FIGURE 4. At the inlet end, the liquid enters the groove 13 cut into the blade, and owing to the fact that the stirring movement 6 (see FIGURE 3) of the viscous mass must take place in the groove 13 of the blade 5 which defines the gap 8, the liquid is conveyed downwards in the direction of the arrow 14, and at the edge i5 it is distributed over the roller 4 and conveyed downwards from groove to groove. By using grooves 13 of this form, it is possible to obtain a high rate of throughput through the apparatus even for very viscous liquids. Moreover, these grooves are very simple to make; they may, for example, be made simply by planing them into the metal sheet before it is curved.

T he liquid moves from the roller 4 (FIGURE 1) into the worm 16 where it is collected and put under pressure. The treated liquid then leaves the apparatus through the pipe 17 where there is a throttle 18 which is so adjusted that the pressure is greater than 1 atmosphere above atmospheric pressure, in order to ensure that the vacuum space 9 will be closed. The pressure is measured on the manometer 19. As the pressure is also dependent on the length of the worm coming into contact with the liquid, the measurement of the pressure serves at the same time to determine the liquid level iii in the worm 16. It is necessary to measure this level, in order to adjust the rate of inflow to the rate of outflow. It is for this reason also that the worm in is provided with threads such that it conveys at a greater rate than the worm 2 for a given speed of rotation. This provides a particularly stable regulation of the liquid level in the evacuation Zone.

The rotation of the roller 4 together with its integrally constructed worms 2 and in can be accomplished by any suitable conventional means, such as for example, by a motor M having a friction wheel W mounted to its shaft S, said friction wheel W being in operative rotary driving engagement with a friction pulley P which is operatively connected to the upper extended portion E of the integrally constructed roller 4 and worms 2 and 16. When the friction wheel W is rotated in the direction of the arrow X, the friction pulley P is rotated in the direction Y, together with the roller 4 and worms 2 and 16.

For purposes of example, the pulley P is provided with a centrally disposed bore B to avoid the need for a rotary connection (not shown) to the heating element 22. To facilitate the introduction of a heat transfer oil into the cavity 21, a passage C is provided through the pulley P.

The roller 4 is provided with a cavity 21 into which a fixed heating element 22 and a thermometer 23 extend. The whole cavity 21 may, for example be tilled with a heat transfer oil which reaches to the level 24. The heat transfer oil is stirred intensively by the rotation of the roller 4 so that there is good heat transmission from the heating element 22 to the roller 4 through the oil in the cavity 21 and hence to the material on the roller. The gases and vapours that have to be removed, enter the vacuum space 9 and are removed by suction through a vacuum pipe 25. It is possible to cool the housing of the evaporator chamber 26 so that the vapours leaving the apparatus are deposited in the form of a condensate which is collected in a collecting channel 27 and conveyed to the atmosphere through a pipe 2-8. The evaporator chamber 26 may, of course, also be provided with heating means to enhance the effect of the internal heating means of the roller. Oils or boiling liquids such as diphenyl may be used as heat transfer media, apart from the usual possibility of connecting the system to a steam supply.

The rotation imparted to the liquid in the wedge shaped gap, the separation of the bubles at the inlet: end and the application of a completely mixed thin layer makes it possible to remove a considerably higher percentage of the solvents, low molecular Weight contents, plasticisers and gases from the liquid.

I claim:

1. A film evaporator for liquids comprising:

(a) A hollow evaporator chamber;

(b) A roller disposed within said chamber and sup- 3 ported thereby so as to be rotatable about its longi tudinal axis, said roller being disposed with its longitudinal axis substantialiy vertical;

(c) Means for introducing a liquid into said chamber and on to the surface of said roller so that said liquid flows downward thereon;

(d) At least one curved blade pivotally supported within said chamber about axis parallel to the longitudinal rotation axis of said roller, said blade being disposed in adjacent spaced relation and curved concavely toward said roller so as to provide a Wedge-shaped gap therebetween, said width decreasing in the direction of roller rotation, said gap having a minimum width which will cause the liquid on the roller surface to become entrained and circulate within said gap and be distributed over the roller surface as said roller is rotated and said liquid flows downward thereon;

(e) Means for rotating said roller;

(f) Spring biasing means connected to said blade for establishing the width at the entrance opening of said gap in response to the forces created by the liquid in said gap; and,

(g) Means for collecting the liquid as it flows down ward oil of said roller, and removing said liquid from the evaporator chamber.

2. The film evaporator of claim 1 wherein grooves are provided in the surface of said blade adjacent to the roller, to facilitate distribution of the liquid over the roller surface, said grooves being obliquely disposed with respect to the pivot aXis of said blade and extending downwardly toward said pivot axis.

3. The film evaporator of claim wherein the means for introducing the liquid into the evaporator chamber Cit and onto the surface of the roller includes a worm auger disposed coaxially above said roller and adjacent thereto, said worm auger having an inlet which is in communication with a liquid supply source, and an annular outlet which discharges liquid onto the surface of said roller in response to the rotation of said auger, and said roller rotating means being also provided for rotating said auger to transfer liquid from the supply source onto the surface of said roller.

4. The film evaporator of claim 3 wherein the means for collecting the liquid as it flows downward off of the roller and removing said liquid from the evaporator chamber includes a worm auger disposed coaxially below said roller and adjacent thereto, said worm auger having an inlet for collecting said liquid flowing down from said roller, and an outlet which communicates with an exit duct provided in said chamber, and said roller rotating means being provided for rotating said worm auger thereby causing it to transfer the liquid collected from the roller out of the evaporator chamber through said exit duct.

5. The film evaporator of claim 4 wherein the worm augers for transferring the liquid in and out of the evaporator chamber are integral with said roller.

References Cited by the Examiner UNITED STATES PATENTS 2,832, 85 3/1935 Zorn et al 159-6 2,804,920 9/1957 Perkins et al 15912 X 2,811,200 10/1957 Montgomery 159-49 2,942,656 6/1960 Rodenacker 159-l2 3,031,030 4/ 1962 Rodenacker.

NQRMAN YUDKOFF, Primary Examiner. 

1. A FILM EVAPORATOR FOR LIQUIDS COMPRISING: (A) A HOLLOW EVAPORATOR CHAMBER; (B) A ROLLER DISPOSED WITHIN SAID CHAMBER AND SUPPORTED THEREBY SO AS TO BE ROTATABLE ABOUT ITS LONGITUDINAL AXIS, SAID ROLLER BEING DISPOSED WITH ITS LONGITUDINAL AXIS SUBSTANTIALLY VERTICAL; (C) MEANS FOR INTRODUCING A LIQUID INTO SAID CHAMBER AND ON TO THE SURFACE OF SAID ROLLER SO THAT SAID LIQUID FLOWS DOWNWARD THEREON; (D) AT LEAST ONE CURVED BLADE PIVOTALLY SUPPORTED WITHIN SAID CHAMBER ABOUT AN AXIS PARALLEL TO THE LONGITUDINAL ROTATION AXIS OF SAID ROLLER, SAID BLADE BEING DISPOSED IN ADJACENT SPACED RELATION AND CURVED CONCAVELY TOWARD SAID ROLLER SO AS TO PROVIDE A WEDGE-SHAPED GAP THEREBETWEEN, SAID GAP WIDTH DECREASING IN THE DIRECTION OF ROLLER ROTATION, SAID GAP HAVING A MINIMUM WIDTH WHICH WILL CAUSE THE LIQUID ON THE ROLLER SURFACE TO BECOME ENTRAINED AND CIRCULATE WITHIN SAID GAP AND BE DISTRIBUTED OVER THE ROLLER SURFACE AS SAID ROLLER IS ROTATED AND SAID LIQUID FLOWS DOWNWARD THEREON; (E) MEANS FOR ROTATING SAID ROLLER; (F) SPRING BIASING MEANS CONNECTED TO SAID BLADE FOR ESTABLISHING THE WIDTH AT THE ENTRANCE OPENING OF SAID GAP IN RESPONSE TO THE FORCES CREATED BY A LIQUID IN SAID GAP; AND (G) MEANS FOR COLLECTING THE LIQUID AS IT FLOWS DOWNWARD OFF OF SAID ROLLER, AND REMOVING SAID LIQUID FROM THE EVAPORATOR CHAMBER. 